Roll

ABSTRACT

A roll, specifically a paper machine press roll, with a hollow rotatable roll body features a roll shell and on at least one of its two ends a hollow roll journal. A guide body which is stationary or fastened to the roll body extends through the interior of the roll body and forms with the roll shell a channel system through which a tempering medium flows. For purposes of using air as tempering medium, a pressure blower and/or a suction blower are connected to the channel system. The channel system and the blower(s) are so dimensioned that an air flow velocity above 10 m/sec will materialize in the channel system.

This is a continuation of application Ser. No. 07/855,273, filed Mar.23, 1992, now U.S. Pat. No. 4,208,955.

BACKGROUND OF THE INVENTION

The invention concerns a roll, preferably a paper machine press roll,which together with a backing roll forms a press gap, and which featuresa tempering device. A roll of this general type is known from DE-OS 2706 850.

The tempering device provided in the interior of such a roll servespreferably to cool the roll shell, however it can also serve to supplyheat to the roll shell. The known roll requires a cooling because it ispart of a metal continuous casting system. Similar rolls serve as pressrolls in papermaking machines. Here, a problem results from the factthat press rolls of that type are provided on their outer shell surfacewith an elastomer coating. During the roll operation together with thebacking roll, heat occurs in the elastomer coating due to the innerflexing work of the elastomer taking place in the area of the press gap,which heat needs to be removed continuously. In this context, allowancemust be made for the fact that rolls of that type are used in a 24-hourcontinuous operation and that in modern papermaking machines everfurther increases of the operating speed and contact pressure are soughtafter.

In the prior rolls, the tempering device is of a design such that coldwater flows along the inside circumference of the roll shell, absorbingheat and leaving the roll again at elevated temperature. The followingproblem occurs in the process: Conditioning the cooling water so that itwill have the required low temperature and the purity necessary forcontinued operation causes high costs. As a further aggravation, thecooling water, despite careful conditioning, can chemically attack theinside surface of the roll shell in a nonpredictable way, due to itscontent of oxygen and/or aggressive ingredients (for instance humicacids). This may be the cause of oscillation crack corrosion and,following thereof, an unexpected break of the roll. On some prior rolls,this risk is avoided by using oil as cooling medium. However, the costsfor conditioning the oil are still higher than those for conditioning ofcooling water. Therefore, oil cooling pays only in rolls with adjustableflexure, where the oil can at the same time serve to transfer the pressforce from the roll shell to a fixed bending axle.

The problem underlying the invention is to advance a roll of the typedescribed in such a way that the tempering (mainly the cooling) of theroll shell will be possible at an expense lower than before, and that indoing so the risk of oscillation crack corrosion will be avoided.

SUMMARY OF THE INVENTION

This problem is solved through the features of the present invention. Aprimary feature of the invention constitutes the use of air as thetempering medium, and dimensioning the channel system (existing betweenthe inside surface of the roll shell and the guide body) along with theblower (s) in such a way that an air flow velocity above 10 m/sec,preferably between 20 and 50 M/sec, will adjust in the channel system.

The inventor has recognized that under the just mentioned conditions ahigh heat transfer from the roll shell to the air or vice versa takesplace, and at that, due to a very large air amount flowing through theroll interior and due to the relatively high heat transfer index. Theadvantages of using air as tempering medium are constituted by the factthat air is available in unlimited quantities and can be conditioned atlow expense (for instance by means of a simple filter) and that air willto a considerably smaller extent than water, or not at all, chemicallyattack the inside surface of the roll shell. Therefore, oscillationcrack corrosion can be avoided at a probability bordering on certainty.

The channel system of the present invention (and provided between theinside of the roll shell and the guide body) may in the simplest case bean annular space, specifically if the guide body has mainly acylindrical shape. However, the guide body may also feature longitudinalribbing or similar spacer elements. In this case, the channel system isformed by a number of channels extending preferably in axial direction.

Previously known from DE-OS 1 070 127 is a so-called expander rollcoolable by means of air and serving the guidance and spreading (i.e.broadside stretching) of webs, for instance paper webs. Thus, this rolldoes not interact with a backing roll. Its roll shell is composed of atubular elastic rubber or plastic shell in which several supportbushings are inserted which in longitudinal direction are arrangedsuccessively. Each support bushing rests by means of two antifrictionbearings on a stationary bent axle. As opposed to it, the inventionalroll is a press roll which (as already mentioned above) forms togetherwith a backing roll a press gap and..- which features a self-supportingroll body; this means that the roll body is supported only on its twoends by means of a bearing each (for instance in a machine frame or inswivel levers). The roll body is comprised (as initially alreadymentioned) of a roll shell and, at each roll end, a hollow roll journalwhich with its outside rests in one of said bearings. Thus, the interiorspace of the roll body is free of installations serving to support theroll body. Consequently, essentially the entire interior space of theroll body is available for a (stationary or concomitantly rotating) airguide body.

Besides, much greater flow cross sections can be provided for thetempering air; thus it is possible to pass at relatively higher air flow velocities and lower expense considerably greater air amountsthrough the roll body than possible in the case of the aforementionedDE-PS 1 070 127. As compared to it, the heat transfer from the rollshell to the air (or vice versa) can thus be considerably increased.Only then does it become possible, for instance when the press rollfeatures an elastomer coating, to continuously remove the high amountsof heat which in the operation of the press roll are generated throughthe flexing work taking place inside the elastomer coating.

The roll body may in known fashion be composed of the roll shell and oftwo hollow roll journals bolted to it which, among others, serve tosupport the roll. In this case, the guide body will normally be insertedin the interior of the roll before the hollow roll journals are boltedto the shell. In many cases, however, using a one-piece roll body isgiven preference, as is known from the initially cited DE-OS 27 06 850.According to this publication, the guide body is made first and servesthen as a core in casting the roll body. In other words: the roll bodyis cast around the guide body and remains thereafter on it.

This complex fabrication process is avoided according to an importantconstructive idea of the invention. When a one-piece roll body is to beprovided it is made first without the guide body, with the outside andinside diameters of the hollow roll journals, the same as heretofore,being smaller than the outside and inside diameters of the roll shell.Besides, the guide body is so fashioned that in an only partiallyprefabricated condition it can be introduced through one of the hollowroll journals into the interior of the roll body and only then becompletely assembled.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments and further favorable developments of the inventionwill be described hereafter with the aid of the rolls illustratedpictorially.

FIG. 1 shows a longitudinal section through a roll with a stationaryguide body (featuring disks);

FIG. 2 and 3 show a longitudinal section each through a roll with arotating guide body;

FIG. 4 shows a cross section along line IV in FIG. 3;

FIG. 5 is a longitudinal section through a further embodiment withrotating guide body;

FIG. 6 shows a cross section along line VI in FIG. 5;

FIG. 7 shows a longitudinal section through a further embodiment with astationary guide body.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The roll illustrated in FIG. 1 (schematically and simplified) is a pressroll for a papermaking machine. A rotatable roll body referenced 10overall comprises a roll shell 11 with an elastomer coating 12 (forinstance of polyurethane) and two hollow roll journals 13, 14. Thelatter have outside and inside diameters smaller than the roll shell 11;they have therefore a conic area by which they are connected with theroll shell 11. Illustrated in all of the FIGS. 1, 2, 3, 5 and 7 is aone-piece roll body. But the invention is applicable also with multiplepart roll bodies where the roll journals are bolted to the roll shell.

The roll body 10 is rotatably supported by bearings 15. Referenced 16overall, a guide body comprises in FIG. 1 a stationary support body 17extending through the interior of the rotatable roll body and restingoutside it on supports 18. The bearings 15 and supports 18, in turn,rest on a not illustrated foundation, machine frame or similar.

Connected with the support body 17 and support 18 is a stationary airsupply housing 19, which is illustrated only schematically and intowhich empties the pressure line 20 of a blower 21. Remaining between thesupport body 17 and the hollow roll journals 13, 14 are annular spaces23, 24 through which the supplied air flows. Several disks 22 arearranged successively on the support body in axial direction. Theiroutside diameter is by a certain amount smaller than the inside diameterof the roll shell 11, so that the air flows at a high velocity above 10m/sec (preferably between 20 and 50 m/sec) through the annular gaps 25remaining between the disks 22 and the inside surface of the roll shell.Besides, the disks 22 create (as illustrated by arrows) a turbulentcondition of flow. Fashioned this way, the tempering device isespecially suited for cooling the roll shell 11 and the elastomercoating 12, which operationally heats up through flexing work. The airsupplied by means of the blower 21, therefore, is preferably cold airtaken in, e.g., from the open or air cooled by means of a coolingdevice. The annular gaps 25 form a "channel system".

The roll body may feature an elastomer coating also in the other FIGS. 2through 4, and 7, but it is not illustrated in these figures. Theinvention is applicable Also in the case of rolls featuring no elastomercoating. In this case it is possible to supply warm air to the temperingdevice, for instance to avoid a "sweating" of the roll shell on itsinside surface, thereby counteracting corrosion. Rolls of that type canbe used as well in papermaking or paper processing machines, especiallyin the dryer section or in a paper coater.

The roll illustrated in FIG. 2 differs from that according to FIG. 1primarily in that instead of a stationary guide body there is a guidebody 26 provided which rotates with the roll body 10. Said guide body iscomposed of a support body 27 which to the roll body 10 is coaxial andpreferably tubular while preferably bolted to the hollow roll journals13, 14 by means of support elements 28 (for instance bolts) arrangedslanted relative to the axis, along with again several disks 22. These,the same as in FIG. 1, are mounted on the support body 27 and form withthe inside surface of the roll shell 11 a series of annular gaps 25. Thesupply of air takes place through a stationary tube 29 and through theone hollow roll journal 13, while the removal of the air takes placethrough the other hollow roll journal 14.

According to FIG. 3 and 4, the disks 22 are mounted on several bars 30of axially parallel arrangement, extending from the one roll journal 13to the other roll journal 14. FIG. 4 shows that each of the disks 22 maybe subdivided in segments 22a through 22d, for instance in foursegments. These segments can individually be introduced in the interiorof the roll body 10 and can be clamped there (for instance by means ofhose clamps 31 welded in place) to the bars 30. Such subdivision of thedisks 22 is a prerequisite for fashioning the roll body 10 as aone-piece component and, e.g., fabricating it by casting.

FIG. 5 and 6 show another embodiment with a one-piece rotatable rollbody 10 where, however, entirely different means make sure that theguide body 36 can be-introduced through one of the two hollow rolljournals 13, 14 into the interior of the roll body and mounted there onit. The guide body 36 has in this case the shape of a hose 35 with acone-shaped bottom 34. Hose 35 and bottom 34 are made of a flexiblematerial allowing their introduction in folded state in the interior ofthe roll body 10. FIG. 5 shows that inside the roll body there areeyelets 37 and eyelets with tension springs 38 arranged, with which thehose 35 is mounted in the roll body in a way such that it will form anessentially cylindrical guide body 36. It goes without saying that forthis purpose there are a number of eyelets 37, 38 distributed across thecircumference. A ring 39 is inserted in the point of the cone-shapedbottom 34. Thus, the bottom 34 can as well be tensioned on the eyelets37 by means of cables 40. The point of the cone-shaped bottom 34 facespreferably toward that roll end (roll journal 13) through which theinflux of air takes place. To ensure a uniform spacing between the hose35 and roll shell 11, spacer elements 41 (for instance knobs or ribs)may be molded or fastened to the outside of the hose 35 which, as thehose is spreading, bear on the inside surface of the roll shell.Channels 25' remain between the spacer elements, forming the channelsystem.

FIG. 6 also shows (exemplary for all embodiments of the invention) thatthe press roll forms with a rotatable backing roll a press gap throughwhich runs, for instance, a still moist paper web 9 along with adewatering felt 8. The purpose of this is to press water out of thepaper web.

In FIG. 5, a drive flange 42 is mounted on the outer end of the hollowroll journal 14, for driving the roll body 10. Air passage openings 43,44 are provided partly in the roll journal 14 and partly in the driveflange 42. Schematically indicated is a stationary air discharge box 45which with openings 43, 44 envelopes the roll end and to which a suctionblower 21' is connected. However, the air feed through the roll may takeplace also in the opposite direction.

FIG. 7 shows a further embodiment with a stationary guide body 46 whichrests on one roll end in a support 18' arranged outside the roll body,and on the other end in a bearing 47 which bears, e.g., in a driveflange 42'. The guide body 46 comprises a (for instance tubular) supportbody 48 and, fastened to it and fashioned of a flexible material, a hose49 which on both of its ends is connected with the support body 48through flexible end walls 50. An air supply line 51 connects to theouter end of the support body 48. Numerous air passage openings areprovided in the part of the support body 48 enveloped by the hose 49.Air discharge openings 53 are provided in one of the two flexible endwalls 50 of the hose 49, but in a small number as compared to the airpassage openings 52 provided in the support body 48.

If such a guide body 46 according to FIG. 7 is to be combined with aone-piece roll body 10, the outside diameter of the tubular support body48 must be smaller than the inside diameter of at least one of thehollow roll journals 13, 14. This makes it possible to introduce thesupport body 48 along with the hose 49 attached to it, but the latterstill in folded condition, through the hollow roll journal into theinterior of the roll. Next, the hose 49 is inflated by means of the airsupplied through the support body 48 and the openings 52. Upon discharge(through the openings 53) from the interior of the hose 49, the air isdeflected; it flows thereafter at first through the annular space 25"and along the inside surface of the roll shell 11, thereafter in thesame direction outward (air discharge 54). Hence, the arrangement mustalways be such that the air discharge openings 53 will be arranged onone roll end and the air discharge 54 from the roll body on the otherroll end. Deviating from FIG. 7, the air passage openings 53 of the hose49 could be arranged on the influx end. In this case, air dischargeopenings would need to be provided in the area of the drive flange 42(as illustrated in FIG. 5 at 43, 44). The support body 46 also may bevaried to the effect that its mounting on the roll body 10 will not bestationary but similar to FIG. 2. Spacer elements may again be providedon the outside of the hose 49, as illustrated in FIG. 5 and 6 at 41.

While this invention has been described as having a preferred design,the present invention can be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. A roll for forming a press gap with a backingroll, said roll comprising:a hollow rotatable roll body having two endsand featuring a roll shell, said roll body including on at least one ofsaid two ends a hollow roll journal; a guide body extending through theinterior of said roll body, said guide body being one of stationary andfastened to said roll body, said guide body and said roll shell defininga channel system through which operationally flows a tempering medium;and blowing means operatively connected to said channel system forsupplying said tempering medium; said channel system and said blowingmeans being dimensioned so that when air is said tempering medium theair may flow through said channel system at a velocity of more than 10m/sec.
 2. The roll of claim 1, wherein said blowing means is at leastone of a pressure blower and a suction blower.
 3. The roll according toclaim 2, wherein said channel system and said blower are dimensioned sothat said air flow velocity is between 20 and 50 m/sec.
 4. The rollaccording to claim 2, in which said roll body includes a hollow rolljournal at each end thereof, wherein said roll shell and hollow rolljournals define a one-piece roll body, the inside diameters of saidhollow journals being smaller than the inside diameter of the rollshell.
 5. The roll of claim 4, wherein each of said disks is subdividedinto segments, said segments being mountable and assemblable inside theroll.
 6. The roll of claim 2, wherein (a) said guide body includes aplurality of disks positioned across the length of the roll and arrangedat least approximately coaxial to the roll body; and (b) the outsidediameter of each disk is smaller than the inside diameter of the rollshell whereby said channel system is defined thereby.
 7. The roll ofclaim 6, wherein said disks are mounted on a stationary support body. 8.The roll of claim 6, wherein said disks are mounted on a support body,said support body being fastened to said roll body.
 9. The roll of claim8, wherein said support body comprises a tube generally coaxial to saidroll body, said support body being fastened to said hollow roll journalby means of support elements arranged diagonally to the axis.
 10. Theroll of claim 6, wherein said disks are fastened to a plurality of barsof axially parallel arrangement, said bars extending from said rolljournal to a second roll journal.
 11. The roll of claim 2, in which theoutside surface of the roll shell features an elastomeric coating, andwherein the temperature of the air supplied as tempering medium is lowerthan the temperature of the roll shell during operation as the rollforms a press gap with the backing roll.
 12. The roll of claim 2, inwhich said rotatable roll body includes a hollow roll journal at eachend thereof, wherein each of said hollow roll journals rests in abearing, said roll body being self-supporting.
 13. A roll for forming apress gap with a backing roll, said roll comprising:a hollow rotatableroll body having two ends and featuring a roll shell, said roll bodyincluding a hollow roll journal at each end thereof, said roll shell andsaid hollow roll journals defining a one-piece roll body, each of thehollow roll journals and the roll shell being respective insidediameters wherein the inside diameters of the hollow roll journals aresmaller than the inside diameter of the roll shell; a guide bodyextending through the interior of said roll body, said guide body beingone of stationary and fastened to said roll body, said guide body beingformed of a flexible material and (a) comprising a foldable hose and atubular support body which extends through the interior of the hose andto which the hose is connected by means of flexible end walls, (b) theinterior of said tubular support body is connected to a compressed airline, and (c) the hose includes air discharge openings; said tubularsupport body including air passage openings situated interior of thehose, said air discharge openings comprising an entire air dischargeflow cross section and air passage openings comprising an entire airpassage flow cross section, wherein the entire air passage flow crosssection is greater than the entire air discharge flow cross section,said guide body further being sized and configured to be insertedthrough one of said hollow roll journals and expanded to a cylindricalbody inside the roll body, said guide body and said roll shell defininga channel system through which operationally flows a tempering medium;and blowing means operatively connected to said channel system forsupplying said tempering medium; said channel system and said blowingmeans being dimensioned so that when air is the tempering medium the airmay flow through said channel system at a velocity of more than 10m/sec.
 14. The roll of claim 13, wherein said hose includes airdischarge openings in only one of the two flexible end walls, saiddischarge openings being positioned so that an air discharge openingfrom the roll body is arranged at the opposite roll end.
 15. The roll ofclaim 14, wherein the outside diameter of the tubular support body issmaller than the inside diameter of the hollow roll journals so that thesupport body, along with the hose contained in folded state, areinsertable into the roll interior through the hollow roll journal.
 16. Amethod for tempering a roll shell of a one-piece hollow roll body,wherein said one-piece hollow roll body is defined by said roll shelland a hollow roll journal at each end thereof, each of the hollow rolljournals and the roll shell having respective inside diameters whereinthe inside diameters of the roll shell, and wherein a guide body extendsthrough the interior of the roll body, said guide body having adiameter, said diameter being larger than the inside diameter of thejournals and smaller than the inside diameter of the roll shell, themethod comprising:introducing a tempering medium into the interior ofthe hollow roll body, and passing said tempering medium at a velocitygreater than 10 m/sec through a channel system in said roll bodyinterior, said channel system defined by said roll shell and said guidebody.
 17. The method of claim 16, wherein said velocity is between 20m/sec and 50 m/sec.
 18. The method of claim 16, wherein the temperingmedium is cold air.
 19. The method of claim 16, wherein said temperingmedium is supplied to the interior of the hollow roll body at least oneof a pressure blower and a suction blower.
 20. A roll for forming apress gap with a backing roll, said roll comprising:a hollow rotatableroll body having two ends and featuring a roll shell, said roll bodyincluding a hollow roll journal at each end thereof, said roll shell andsaid hollow roll journals defining a one-piece roll body, each of thehollow roll journals and the roll shell having respective insidediameters wherein the inside diameters of the hollow roll journals aresmaller than the inside diameter of the roll shell; a guide bodyextending through the interior of said roll body, said guide body beingone of stationary and fastened to said roll body, said guide body andsaid roll shell defining a channel system through which operationallyflows a tempering medium, said guide body including a plurality of diskspositioned across the length of the roll and arranged at leastapproximately coaxial to the roll body, the outside diameter of eachdisk being smaller than the inside diameter of the roll shell so thatsaid channel system is defined thereby, each of said disks beingsubdivided into segments, said segments being mountable and assemblableinside the roll; and blowing means operatively connected to said channelsystem of supplying said tempering medium; said channel system and saidblowing means being dimensioned so that when air is the tempering mediumthe air may flow through said channel system at a velocity of more than10 m/sec.